The basic aim of the proposed research is to carry out a longitudinal follow-up study of men and women in their middle and late twenties who had been participants in an intensive, four-year, longitudinal study during their adolescence and youth. Over 600 participants were involved; 432 had been in junior-senior high school during the years of the earlier study, and 205 had been in college. On the basis of four, successive annual questionnaires, a large amount of developmental information was collected in the areas of alcohol use and drug use, of sexual behavior, and of general deviance such as lying, stealing, and aggression, and also in the areas of personality and social environmental factors relevant to such behavior. The research was guided by and served to test a social- psychological theory of problem behavior in youth. The proposed research has involved recontacting these participants and resuming the assessments by questionnaire. The assessments again cover personality, the social environment, and behavior, with intensive concern for alcohol and drug use, problems associated with that use, attitudes toward alcohol and drugs, and the availability of both. Fully 94% of the former participants have already cooperated in the first wave of the follow-up study, filling out a 65-page questionnaire. The next wave of data collection, scheduled for summer 1981, will complete the panel study design within young adulthood. The research, being longitudinal in nature, predicated on an earlier longitudinal study, and focused on men and women going through the high-risk years of the twenties, should illuminate that unexplored period of the life span. It should also make clear whether alcohol and drug use in young adulthood are signalled by and predictable from personality and behavior during adolescence and youth.